Primary science assessment item setters' misconceptions concerning biological science concepts

Identified Misconceptions

2.1 Breathing and Respiration

Within the primary science syllabus, the subject matter of breathing and respiration is introduced progressively from Primary 3 (P3) to Primary 5 (P5). In P3, pupils are introduced to the concept that living things need air, water and food to survive; they are taught life cycles of plants and animals. The respiratory and circulatory systems of human beings, and plant parts and their functions are introduced in P4. Thus by the end of P4 pupils learn the different structures and organs used by plants and animals to exchange gases with the environment as well as the function of transport system in plants and circulatory system in human beings. At the P5 level, pupils learn about the processes of photosynthesis and respiration. They learn that photosynthesis is the process in which plants make food by combining water and carbon dioxide from the environment in the presence of light energy. They learn that oxygen is also produced during the process of photosynthesis. They also learn that food produced by plants becomes the source of energy for animals and other types of organisms; and that respiration is a process occurring in living cells, and by which energy is released from food and made available for life processes such as movement, growth, repair, and so forth.

In the syllabus, differentiation is made between respiration and breathing, that is,

Breathing refers to the process that brings about an exchange of gases between the organism and its environment; and

Respiration refers to the process that releases energy from food substances in living cells

At the primary level the distinction between breathing as a physical process and respiration as a chemical process is not made.

However, many question setters (teachers) set questions which show confusion between these two processes.

Example Question 1 illustrates the confusion in the question setter's mind. The intended answer is Option 1- lungs. The question stem refers to respiration whereas the options provided and the intended answer are specifically parts concerned with breathing or the process of that brings about gaseous exchange between organisms and their environment.

One possible cause of this particular misconception could be the universal use of the term "respiration" to refer to aspects concerning the breathing system - particularly in human biology and medicine where the nostrils, windpipe, lungs together with the mechanical actions of the diaphragm and rib cage are referred to as the respiratory system and lung diseases such as bronchitis and pneumonia are termed respiratory ailments.

An incomplete understanding of breathing is shown in Example Question 2 which is also taken from the P4 level. In this example the intended answer is option 4. However, what is breathed out is not just carbon dioxide. The correct concept is that the air that is breathed in is relatively rich in oxygen (about 21%) and poor in carbon dioxide (about 0.03) whilst the air that is breathed out is poorer in oxygen (about 16%) but richer in carbon dioxide (about 4%).

2.2 Plant Reproduction

Life cycles of plants and animals are introduced at the P3 level and pupils should be engaged in practical activities to grow plants from seeds in order to observe the complete plant life cycle. The topic is revisited at P5 when pupils study the various reproductive processes employed by plants including sexual reproduction of flowering plants.

In testing pupils on the diverse methods of seed dispersal used by different plants, often question setters will refer to'fruit dispersal' rather than the correct concept of 'seed dispersal'. This appears to suggest that fruits have been misconceived as having the potential to develop into new plants, when in actual fact, fruits either get eaten or decomposed. It is the seed that has the potential for growing into new plants. This conceptual error is illustrated in example question 3, where the intended answer is option 1. The root cause of this error is likely to be the influence of simple perceptual reasoning: an animal eats the fruit or the fruit splits and ejects the seeds.

Another related problem concerns a prevailing misconception that, in the life cycle of a flowering plant, the fruit develops before the seeds. The correct concept is that upon union of the female gamete (in the ovule) with the male gamete (from the pollen), the seed is formed, and only after that, the fruit develops from the ovary. In other words, the fruit is developed only after the process of fertilization which results in the seed formation, as a by-product of the reproductive process. The fruit develops to protect the seeds, and in some cases, develop to become "attractive" to animals that will be the agents of seed dispersal. This misconception is shown in Example Question 4 taken from a P6 paper

The same misconception is shown in Example Question 5, also from a P6 paper. In this question the intended answer is option 4 when in actual fact, none of the options is correct.

The option that is closest to the correct answer would be option 3, which should be modified by removing "fruits" completely and drawing an arrow from "seeds" to "seedlings" as shown in Figure 1 below to make it acceptable as the answer key.

2.3 Cell Structures and Mechanisms

Cell Structures and mechanisms are covered at the P5 level. The learning objectives are identification and understanding of function of the parts of plant and animal cells and the understanding of organism growth through cell division. Even within this quite limited subject scope questions involving cell structures and mechanisms show a number of misconceptions amongst question setters. Example Question 6 which asks for the common parts found in all cells, the intended answer is option 4 indicating that all cells have cytoplasm, cell membrane, nucleus and cell sap. However, not all cells have nuclei, examples being bacterium cells and red blood cells of human beings. Also, not all cells have cell walls; examples being animal cells. This misconception illustrates one of the problems with biological systems as compared to physical systems and that is the greater scope for variability and exceptions within broad categories and therefore the problem of using terms like 'all' and 'every' in biology MCQ test items. Whilst the generalizations are useful at a macroscopic level, the scope for variation from the general case is great and many pupils will be aware of the typical exceptions.

In example question 7, the intended answer (option 1) suggests an over-simplification of cells structures. Here the question setter appears to think that the cell size in whales is more or less the same as that in the housefly. There appears to be a lack of understanding of the diverse cell structures and functions in multi-cellular organisms, and that it is meaningless to make a gross comparison of cell sizes in two such dissimilar multi-cellular organisms.

2.4 Human Systems

In addition to the misconception regarding breathing and respiration mentioned earlier several other aspects of human systems give rise to difficulties amongst question setters. Different aspects of human systems are introduced at stages throughout the primary science curriculum. Digestive and muscular/skeletal systems are covered in P3, respiratory and circulatory systems in P4, reproduction in P5 along with greater depth of understanding of respiration.

The most common problem is that question setters appear to take a one dimensional view of the different systems and often fail to appreciate the necessary levels of inter-working between systems that take place in order for the body to function.

This one dimensional view is illustrated in Example Question 8 taken from a P3 paper. The teacher's intended answer is option 2 - indicating that only the muscular and skeletal systems interact to enable movement. Most pupils will recognize that all of these systems interact in some way to enable movement. The skeletal system provides the anchorage for the muscles from which they can exert contraction; the digestive system is just as important as the respiratory system in providing muscle cells with the raw materials for the energy release that powers the muscles.

A similar one-dimensional view appears to be the problem in Example Question 9, from a P5 paper. The question setter's intended answer is option 2 - indicating that no muscles are working at the end of the run. However, at the end of the exercise run, the chest will be heaving, the diaphragm moving and the heart pumping - these are parts of the muscular system. Therefore, none of the statements is false and so no correct answer key is available. The problem identified in questions 8 and 9 is not really one of misconceptions, but rather one of poor item crafting as discussed in the following section under "Discussion". Perhaps question 8 could be crafted in a tighter, more specific way such as: "Which of the following systems act as levers to enable us to move?"